Electronic thermometry apparatus for measuring a patient's body temperature orally, rectally or axillarily via a temperature probe have been in common use in doctor's offices, clinics, hospitals and other health care facilities for many years. Typically, such medical thermometers include an axially elongated, cylindrical temperature probe having a temperature sensing element, commonly a thermocouple or thermistor, disposed within a distal tip of the probe. The temperature probe is tethered to a base housing by a flexible cord and the temperature sensing element is connected by signal conductive wires passing through the flexible cord to a processor carried in the base housing. The processor, conventionally a microprocessor, includes software for processing signals received from the temperature sensing element of the temperature probe to accurately estimate the patient's temperature. The patient's temperature is then displayed on a display, such as a LED display, carried on the base housing. Electronic thermometers of this type are disclosed in U.S. Pat. Nos. 5,632,555; 6,000,846; 6,036,361; 6,827,488 and 6,971,790, the entire contents of which are incorporated herein by reference, and are commercially available from Welch Allyn, Inc, the common assignee of the aforementioned patents and the assignee to which this application is subject to assignment.
For hygienic reasons, it is customary practice to place a sterile disposable probe cover over the temperature probe prior to each use. The purpose of the disposable probe cover, which is discarded after a single use, is to prevent cross-contamination between patients. If the temperature probe were used without a new sterile disposable probe cover for each use, the temperature probe would have to be sterilized between each use, therefore limiting the application and practicality of the portable electronic thermometer, particularly in multi-patient health care facilities. Conventionally, such temperature probe covers are elongated, hollow plastic sheaths molded to conform to the shape of the temperature probe.
When a patient's temperature is to be measured rectally, care must be taken to ensure that the probe is not inserted too deeply. If penetration is excessive, the temperature sensing elements in the probe tip will likely not be properly positioned in the rectum, which will result in an inaccurate temperature measurement. Further, if the probe is inserted too deeply, particularly with respect to infants, the probe might damage rectal tissue. Typically, the temperature probe would be inserted only about 1.5 centimeters (about ⅝ inches) into the rectum for adults, less for infants and children.
To facilitate use of the temperature probe in rectal applications, some probe covers are provided with an over-insertion indicator. For example, U.S. Pat. Nos. 4,159,766 and 6,957,911 each disclose a temperature probe having an exterior over-insertion indicator. U.S. Pat. No. 4,159,766 discloses a cover for a temperature sensing probe having a shoulder on the exterior of the probe cover set back axially from the distal tip of the probe a preselected distance commensurate with the desired penetration depth for rectal applications. U.S. Pat. No. 6,957,911 discloses an infant thermometer whose probe includes a flexible annular flange disposed on the exterior of the probe axially inwardly from the probe tip to indicate the correct depth of insertion for rectal application on infants.
In practice, a patient's temperature is often taken, whether orally, rectally or axillarily, in a dimly lighted room or at night in a multi-patient room or ward where it is desirable to maintain a low level of lighting to avoid disturbing other patients. Inadequate lighting may also be a problem when taking a patient's temperature rectally even in a relatively well lighted room. In U.S. Pat. No. 6,886,979, a temperature measuring device is disclosed wherein a light in the handle of the device illuminates the area in front of the probe and a region of the temperature probe immediately axially inward of the probe tip which is made of a luminescent material or ink to facilitate use in the nighttime or low level lighted environments.